Fluted or corrugated panels have a wide range of applications. They are generally used as an economical alternative to solid sheet panels, as they have an extraordinary strength to weight ratio, with much greater insulating properties than solid sheet panels—that is if the ends of the fluted panels are closed. The fluted panels, which can be extruded from high-density polypropylene or polyethylene are more durable than corrugated fiberboard, lighter than wood, and impervious to water and can withstand harsh chemicals. For instance, fluted thermoplastic panels can be used to form reusable containers and boxes, displays, screen printings, automotive interior components, storage cabinets, walls, supports, etc. Transparent fluted panels also can be used as skylights, wall dividers, etc.
Such a fluted panel typically comprises a pair of spaced apart thermoplastic layers or skins interconnected with longitudinally extending ribs or flutes that form longitudinally extending interior passageways, as illustrated in U.S. Pat. No. 5,658,644, the disclosure of which is incorporated herein by reference. The flutes are uniformly spaced apart and run in one direction for the entire length or width thereof. The flutes, however, can run in any direction and can be angled. The cross section of the panel having perpendicular flutes looks like a series of side-by-side square tubes having open ends, which will allow air, liquid or any material to flow freely inside the length of the panel. Such fluted panels are commercially available from INTEPLAST GROUP, LTD of Livingston, N.J. (sold under the name of IntePro®, as advertises at http://www.worldpak.com) and COROPLAST, INC. of Dallas, Tex. (sold under the name of Coroplast™, as advertises at http://www.coroplast.com). These companies manufacture thermoplastic panels in various sizes and thickness, ranging from 2 mm to 13 mm, with the skin thickness ranging from 6.5 mil to 36 mil and the flute thickness ranging from 6.5 mil to 29 mil. These panels, however, come with open ends (at four sides for square or rectangular shape), which limit their use.
The problem with open ends is that they allow dirt and water to collect inside. Moreover, the open edges can be sharp, making it unsuitable for consumer use, as the sharp edges can catch and scratch skin and clothing. Further, the open edges can be unsightly, making it esthetically undesirable. Thus, it would be desirable to close the open ends. Indeed, properly closing and sealing the ends and making them more esthetically appealing would greatly extend the use of such panels. The insulating and inert (non-reactive) properties of sealed thermoplastic panels are highly desirable qualities. Because the extruded polypropylene is highly non-reactive, it is qualified for medical use, which makes the panels an excellent candidate for food, pharmaceutical, medical storage, and packaging applications. Presently these thermoplastic panels have limited uses, as there is not an economical solution for sealing and finishing the edges. Other markets that could benefit from the fluted panels if the edges are sealed are, for example, storage, cabinetry, casework, and furniture industries.
Currently there are two methods of finishing or sealing the ends of extruded plastic materials. The first finishing method is covering the open ends with either an unlike or like material. This first method involves fitting the panels in U-shaped channels. An example of this is the current method for finishing skylights and divider panels, where the open ends are capped with U-shaped channels of like material. This method is labor intensive and may need to rely on bonding agents to securely attach the channels. The bonding alternative is not only expensive, it requires a long curing period, and the result is not all that esthetically pleasing.
The second method involves heating and stamping the flat sheets at the portion of the skins that overlap with a die to press and fuse them together. This method seals the edges together very well. But the tooling required to make the die is very expensive and limited to a single shape. This method makes shorter productions unpractical. This method is also not suited for producing esthetically pleasing ends for consumer products because the resulting ends are fairly sharp, which can scratch skin and clothing.
Accordingly, there is a need for an economical solution for producing an esthetically pleasing end in the current fluted panels. The present invention addresses this need.